A popular upgrade to allow more lift or accommodate a more aggressive roller camshaft when using traditional Small Block Chevrolet heads is to retrofit them with LS-style valve springs. This tool will allow customers to machine their cylinder heads for the correct diameter valve spring. Two versions are offered, a 1.340″ seat cutter for 0.500″ guides and a 1.340″ seat cutter for 0.560″ guides. The durable carbide cutting tip material ensures precision and accuracy. The cutter requires the use of an arbor pilot, which is available in four different sizes.